Keyer circuit for an electronic musical instrument wherein a single switch may actuate a single note or a chord

ABSTRACT

A chord circuit is provided in which, upon positioning of a tab switch, the actuation of a given key will cause the sounding of a predetermined chord. Such chord circuits may be provided for a number of different chords, so that depending upon the tab switch which is operated, the actuation of the C key, for example, may cause the sounding, selectively, of C major chord, C minor chord, C diminished chord, and so forth. In the present circuit this is done without requiring the ganging of switch poles, so that the same single-pole key switch which is conventionally used to sound a given tone, also sounds the various preselected chords.

United States Patent Brand et al.

[ 51 May 23, 1972 [54] KEYER CIRCUIT FOR AN ELECTRONIC MUSICALINSTRUMENT WHEREIN A SINGLE SWITCH MAY ACTUATE A SINGLE NOTE OR A CHORD[72] Inventors: John R. Brand, Northridge; Ernest A.

Smith, Santa Monica, both of Calif.

[73] Assignee: Warwick Electronics Inc., Chicago, 111.

[22] Filed: Nov. 27, 1970 [21] Appl. No.: 93,328

[56] References Cited UNITED STATES PATENTS 3,548,066 12/1970 Freeman..84/1.03 3,590,129 6/1971 Freeman ..84/l.0l

46 ts KS E TG E2 TG 0 KS (firs a --A K8 are F2 re} a c Ks ATG -A Ks crcPrimary Examiner-Lewis H. Myers Assistant Examiner-Smiley J. WitkowskiAttorney-Jessup & Beecher ABSTRACT A chord circuit is provided in which,upon positioning of a tab switch, the actuation of a given key willcause the sounding of a predetermined chord. Such chord circuits may beprovided for a number of different chords, so that depending upon thetab switch which is operated, the actuation of the C key, for example,may cause the sounding, selectively, of C major chord, C minor chord, Cdiminished chord, and so forth. In the present circuit this is donewithout requiring the ganging of switch poles, so that the samesingle-pole key switch which is conventionally used to sound a giventone, also sounds the various preselected chords.

5 Clains, 9 Drawing Figures MAJOR CHORD MAJOR CHORD s3 7 E s B 87 FKSMAJOR CHORD Patented May 23, 1972 3,665,088

4 Sheets-Sheet 2 INVENTORS.

m mDm ERNEST A. SMITH FL W FL FL G TG B TG

A TG

DTG

To VOICING 568 JOHN R. BRAND 8 JESSUP a BEECHER ATTO EYS PEDAL DIVIDERPatented May 23, 1972 4 Sheets-Sheet .'1

+8 FIG. I I O 2 GENERATOR 700 1 F -l20 7850 g 17 I76 I74 I80 FIG. 5.

+8 TONE FL 226 GENERATOR TONE o 376 GENERATOR v 32 F1 s5o' T F/6.7. ll,+8 +|o TONE 0 GENERATOR 426 ATTO NEYS Patented May 23, 1972 3,665,088

4 Sheets-Sheet 4 FIG 8 -|0 O 576 T ToNE -IO 534-- GENERATOR I l N 550526 540 SI j 542 558 HVOICINGI u 562 FIG. 9. 620

ToNE GENERATOR fi TONE GENERATOR INVENTORS.

JOHN R. BRAND a ERNEST A. SMITH JESSUP 8 BEECHER INSTRUMENT WIIEREIN ASINGLE SWITCH MAY ACTUATE A SINGLE NOTE OR A CHORD DESCRIPTION OF THEDRAWINGS FIG. 1 shows the circuit of the present invention in its basicform, wherein actuation of a given single-pole key switch may cause thesounding of a given chord, shown in this example as the major chord.

FIG. 2 shows a modification in which the preselected note is sounded,even though the chord tab switch is not actuated.

FIG. 3 shows a refinement in which the pedal tone corresponding to theactuated key switch is also sounded.

FIG. 4 is a fragmentary circuit diagram, showing the manner in which PNPtransistors may be employed instead of diodes.

FIG. 5 corresponds to FIG. 4 employing instead P channel J field effecttransistors instead of diodes.

FIG. 6 is similar to FIG. 4 employing P channel J field efi'ecttransistors with no loading on the tone generator.

FIG. 7 is similar to FIG. 4 employing N channel J field effecttransistors instead of diodes.

FIG. 8 illustrates the employment of an MOS integrated circuit in placeof both the diodes and the resistors.

FIG. 9 illustrates a modification in which integrated circuits areemployed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, representsa tone signal generator at the output 22 of which appears a square wave,shown at 24. In this example it will be assumed that the negativeexcursion is at zero volts (ground) and the positive excursion at plus 8volts.

The tone signal 24 is coupled via a diode gate 26 to point 28, whichserves as the output terminal of the gate 26 and also its controlterminal.

It is to be understood that the circuit includes tone generators for alldesired tones. For example, tone generator 20 will be assumed togenerate the C tone; tone generator 30 the D tone; tone generator 32 theE tone; tone generator 33 the F note; tone generator 35 (FIG. 3) the Gnote; and similar tone generators (not shown) generating the A, A0, B,C0, D0, F0, G, G0 notes. and so on.

Each tone generator has a corresponding key switch actuated customarilyby the finger keys of an organ keyboard. Moreover, each of the tonegenerators supplies its tone to other key switches, as will bedescribed, when its tone is included in the chord represented by theparticular key switches. Each key switch consists of a single-pole,doublethrow switch represented by the switch 34 for the note C. Insimilar fashion, the D tone generator 30 has a key switch 36; the E tonegenerator 32 has a key switch 38 the F tone generator 33 has a keyswitch 87; the G tone generator 35 has a key switch 89 (FIG. 3), and soon.

The key switch 34 is coupled to a number of different tone generators.In the example shown, these are the tone generators for the C majorchord, namely C, E and G. Thus the switch 34 is coupled via resistor 40and conductor 41 to the output terminal 28 of the C gate 26. Switch 34,and more specifically the pole of switch 34, is also coupled viaresistor 42 and conductor 44 to the gated output 46 of the E tonegenerator 32. The major chord is completed by coupling the switch 34 viaresistor 48 to the output of the G gate (not shown).

The normally closed contact 50 of the key switch 34 is grounded at 52.The normally open contact 54 is connected via conductor 56 and couplingcapacitor 58 to an output circuit terminal 60. The output circuit may beof any form, simple or complicated, and is here shown by way of exampleas consisting of a voicing circuit 62, an amplifier 64, and anelectro-acoustic transducer in the form of a speaker 66. The conductor56 is biased by a voltage source 68 through resistor 70.

As noted hereinbefore, terminal 28, in addition to constituting theoutput terminal of the diode gate 26, also constitutes the controlterminal for the gate. This control is efi'ected through the selectiveapplication or removal of bias from a source 72 applied through adouble-throw switch 74 to a chord control line 76, and thence through anisolating resistor 78 to the terminal 28. When the switch 74 is in itsupper position, or A position, it engages contact 80 and is grounded.When in its lower or B position, it engages contact 82 and places theline 76 at the bias of 72. In the example shown, this bias will beassumed to be plus 6.6 volts.

When the tab control switch 74, which controls the selection of thechord, is in the upper or A position, the voltage at 28 remains at zerovolts, as shown at 84. When the chord tab.

switch 74 is in its lower or B position, the signal is as shown at 86,being a square wave going between 6.6 and 0.6 volts. That is, when thetone signal 24 is at plus 8 volts, the diode 26 can, of course, notconduct, since it is reverse biased. During this interval then, the fullvoltage from 72 is felt at 28 and accounts for the 6.6-volt level of thesignal 86. When the tone signal 24 drops to zero volts, then currentflows through the diode 26 and the resulting voltage drop acrossresistor 78 is felt at 28. The forward voltage drop across the diode 26is approximately 0.6 volts, so that the minimum voltage excursion at 86is thus 0.6 volts; thus, with the chord tab switch 74 in the B position,there resides on the terminal 28 a square wave tone signal having apeak-to-peak excursion of approximately 6 volts.

This tone signal is applied via the conductor 41 and resistor 40 to thepole of switch 34.

Thus, whenever the switch 74 is in its lower or B position, thereresides on the pole of the C key switch 34 tone signals corresponding tothe notes C,E and G, i.e., a C major chord. The actuation of the C keyswitch 34, i.e., the closing at contact 54, thus places a C major chordon the conductor 56 and thence via the capacitor 58 to the loudspeaker66.

The C tone signal from 20 is also fed to the other key switches whosemajor chord incorporates the note C. Thus, the terminal 28 is coupledvia the conductor to the key switch 87 representing the note F on thekeyboard. The C note from terminal 28 is coupled also via conductor 88to the key switch for G sharp (not shown), since a G sharp major chordalso contains the note C. In like manner, each of the tone generators,as exemplified by the C tone signal tone generator 20, is coupledthrough its associated diode gate, to respective key switches whichrepresent chords in which the particular note from that tone generatorappear.

In the fashion above described, each of the key switches exemplified by34 is coupled to the gated output of the three tones making up the majorchord for that key. Reciprocally, and as explained above, each of thetone generators has its output applied to each of the key switches whichneeds that tone in its major chord. When the chord tab switch 74 ismoved to its lower or B position, the actuation of any key switch willthus cause the sounding of a major chord of that key. When the chord tabswitch is in its upper or A position, no tones will sound upon theactuation of a key switch, because all of the gates exemplified by diodegate 26, are disabled by the removal of enabling bias from the source72.

It is usually desirable to always allow the actuation of a given keyswitch to sound that particular note. To that end the circuit of FIG. 2is provided, in which the conductor 41 instead of being connected to thegated output 28 from the tone generator 20, is connected directly to theoutput terminal 22. Thus, in FIG. 2, actuation of the key switch 34causes a sounding of the note C, irrespective of the position of thechord tab switch 74. In FIG. 2, with the switch 74 in the A position,the actuation of a given key switch, e.g., 34, will sound only thatparticular note. With switch 74 in the B position, the actuation of agiven key switch will sound the major chord of that key.

It will be obvious that similar matrixes can be provided, each with itsindividual chord tab switch 74, to provide other chords of a given note,for example, the minor chord, the diminished 7th etc.

In FIG. 3 the circuit is shown expanded to include a pedal divider 90,whose output 92 is applied to the output conductor 56. The pedal divider90 is known in the art and is simply a frequency divider which deliversto its output a signal of onehalf of the input frequency. This frequencythen becomes the pedal tone corresponding to the note of the actuatedkey switch 34.

The input to the divider 90 is taken from the diode output terminal 28via another diode gate 94 and coupling capacitor 96. The terminal 98constitutes both the output terminal for the second diode gate 94 andthe control terminal which serves to selectively enable and disable thegate 94.

The diode gate 94 is enabled by the closing of key switch 34, whichapplies enabling bias from a 6-volt bias source 68 to the lower,normally open, contact 54 of the key switch 34.

When the chord tab switch 74 is in the B position, tone signal resideson the terminal 28. Since this signal, however, varies between plus 0.6and plus 6.6 volts, it is not felt at the terminal 98, because of thepolarization of the diode 94. With closing of the key switch 34, the6-volt, bias from 68' appears on terminal 98 via resistor 100, so that a4.8 volt, peak-topeak square wave now resides on the output terminal 98,i.e., a square wave varying from 6 volts to 1.2 volts.

This square wave is differentiated in the capacitor 96 and the resultingnegative spikes on the conductor 60 are used to drive the pedal divider90 to produce a square wave output at 92 having one-half the frequencyof the tone generator 20.

FIGS. 4, 5, 6 and 7 illustrate respective modifications of the presentinvention, in which the diode 26 has been replaced by variousthree-terminal devices. In these figures the reference numeral for agiven component has been given a distinctive number in the hundredsposition. The last two digits indicate the correspondence between themodification and the component shown in FIG. 1. Thus, in FIG. 4 thenumeral 126 denotes a transistor (three-terminal device) which replacesthe diode 26 (two-terminal device) of FIG. 1. Essentially the differenceis that in the FIG. 1 modification the control terminal for the gaterepresented by the diode 26 is the same as one of the two signalterminals. In the three terminal components of FIGS. 4-7, the gateterminal is separate from the two signal terminals.

In FIG. 4, the diode 26 has been replaced by a PNP transistor 126. InFIG. 5, the diode has been replaced by a P channel J-FET. In FIG. 6 thediode has been replaced by a P channel J F ET with no loading on thetone generator 320. In FIG. 7 the diode has been replaced by an Nchannel J FET.

FIG. 8 illustrates the integration of diode and resistors into an MOSintegrated circuit. Keeping in mind the numerical format explainedabove, it is believed that the substitution of components from FIG. 1 toFIG. 8 will be obvious.

The tone generators 20 et al may also be included within a single ICchip. In this case the production of the monophonic bass note is done ina slightly different way when IC chips are used. This is shown in FIG.9, where an extra divider per note is included within the IC and asecond equivalent of diode 26 is used to produce a polyphonic basssystem that does not produce burble. These two diodes are shown at 626and 626 in FIG. 9. While FIG. 9 illustrates the tone generator 620 asbeing one octave lower than 620, it will be readily understood that itcould just as well be more than one octave lower by the incorporation ormultiple dividers.

It will be readily understood by those skilled in the art that theoblique line exemplified at 700 in FIG. 4 represents the common bussingof all notes of the circuit. That is to say, referring to FIG. 4 by wayof example, the conductors 176 leading from their respective tonecircuits are all connected to a common bus at 700 and thus employ acommon switch 174.

What is claimed is:

1. Keying circuit for keyboard musical instrument having a plurality oftone signal generators for generating electrical signals respectivelycorresponding to different musical notes, electroacoustic transducingmeans for sounding said notes, a plurality of key switches coupled tosaid transducing means and to said tone signal generators for applyingrespective electrical signals to said transducing means, characterizedby:

circuit means, including gate means respectively connected to saidgenerators, for coupling a plurality of said generators corresponding tonotes of a chord to a given one of said key switches, to be applied tosaid transducing means upon actuation of said one of said key switchescorresponding to one of said chord notes, and

control means connected to said gate means for selectively enabling anddisabling said gate means to selectively effect sounding of a chord uponactuation of said corresponding switch. I

2. Circuit in accordance with claim 1, including:

bypass circuit means for bypassing the gate means for said correspondingswitch to the generator corresponding to said one note,

whereby said one note is sounded upon actuation of said correspondingswitch, irrespective of the enabling or disabling of said gate means.

3. Circuit in accordance with claim 1, wherein:

said gate means comprises non-linear conducting means,

said generators generate essentially rectangular waves, and

said control means comprises means for selectively biasing said gatemeans to non-conductive and conductive condition.

4. Circuit in accordance with claim 1, including:

frequency divider means having input and output,

means for coupling said output to said transducing means,

and

second circuit means coupling tone signals from said circuit means tosaid input, for sounding a pedal tone whenever the key switchcorresponding to the pedal tone is actuated.

5. Circuit in accordance with claim 4, wherein said second circuit meansincludes:

second gate means coupled to said first-named gate means and whereinactuation of said corresponding key switch enables said second gatemeans, thereby to effect sounding of said pedal tone.

1. Keying circuit for keyboard musical instrument having a plurality oftone signal generators for generating electrical signals respectivelycorresponding to different musical notes, electroacoustic transducingmeans for sounding said notes, a plurality of key switches coupled tosaid transducing means and to said tone signal generators for applyingrespective electrical signals to said transducing means, characterizedby: circuit means, including gate means respectively connected to saidgenerators, for coupling a plurality of said generators corresponding tonotes of a chord to a given one of said key switches, to be applied tosaid transducing means upon actuation of said one of said key switchescorresponding to one of said chord notes, and control means connected tosaid gate means for selectively enabling and disabling said gate meansto selectively effect sounding of a chord upon actuation of saidcorresponding switch.
 2. Circuit in accordance with claim 1, including:bypass circuit means for bypassing the gate means for said correspondingswitch to the generator corresponding to said one note, whereby said onenote is sounded upon actuation of said corresponding switch,irrespective of the enabling or disabling of said gate means.
 3. Circuitin accordance with claim 1, wherein: said gate means comprisesnon-linear conducting means, said generators generate essentiallyrectangular waves, and said control means comprises means forselectively biasing said gate means to non-conductive and conductivecondition.
 4. Circuit in accordance with claim 1, including: frequencydivider means having input and output, means for coupling said output tosaid transducing means, and second circuit means coupling tone signalsfrom said circuit means to said input, for sounding a pedal tonewhenever the key switch corresponding to the pedal tone is actuated. 5.Circuit in accordance with claim 4, wherein said second circuit meansincludes: second gate means coupled to said first-named gate means andwherein actuation of said corresponding key switch enables said secondgate means, thereby to effect sounding of said pedal tone.